• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.197-206
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• 2002

The purpose of this study was to investigate the putter head movement during the putting strokes. Highly skilled 5 golfers(less than 3 handicaps) and 5 novice golfers(having no golf experience) participated in this study. A target distance was 3 m. Movements of the putter head were recorded at 60 Hz with two video cameras. The results showed that the novice golfers moved the club significantly longer than the expert golfers(p<.0001). Accoring to a movement time, novice golfers moved their club significantly faster than the expert golfers(p<0.001). Novice golfers could not control the club head effectively, and could not hit the ball correctly. Based on the impact zone movement, sweet spot of novice golfers moved faster(along the line of putt), higher(along the vertical line), and wider(along the side to side line) than that of expert golfers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.127-135
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• 2006

In this study, steel deck bridges are chosen as analytic model to show the structural behaviors generated by high temperature of pavement and to formulate the simplified approximate analysis of thermal effects. In general, the thermal effect is changed by the material property of pavements and environmental temperature as well as shape, size and boundary conditions of bridge. Specially, this effect is the representative initial stress problem dependent on time. The thermal effect, however, does not depend on time and thermal effect is regarded as initial load in this study. After these thermal loading is modelled as moving loads, influence lines of reactions of shoes are calculated and the successive pavement steps with arbitrary segments are determined to minimize the thermal effect of shoes by influence line.

• Korean Journal of Materials Research
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• v.6 no.9
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• pp.905-918
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• 1996

초전도 마그네트 구조용 부재로 최근 개발된 오스테나이트계 스테인레스강 JN1 모재, GTA 용접부 및 열처리재에 대한 기계적 성질을 조사하기 위해 실온(293K)에서 극저온(4K)까지의 온도에서 소형펀치(Small Punch)시험을 실시하였다. GTA 용접부의 용융선 근방의 극저온 기계적 성질은 모재와 용접금속에 비해 크게 저하하였다. 4K에서 실험된 용융선 시험편으로 얻어진 하중-변위곡선상에서 부하의 초기 단계에 보통의 서레이션과 다른 pop-in이 관찰되었고, 이때 시험편 표면의 용융선 근처에서 약 0.1-1mm 정도의 크랙이 발생하였다. 열처리재의 기계적 성질은 열처리 시간과 온도의 증가 또는 시험온도의 저하에 따라 크게 저하되었다. 위의 결과에 기초하여 본 연구에서 실시한 소형 시험편을 사용하는 SP 시험법은 극저온에서 JN1 강의 모재와 열처리재뿐 만 아니라 GTA 용접부의 기계적 성질을 평가할 수 있는 유용한 시험법이었다.

• Journal of KIISE:Software and Applications
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• v.36 no.11
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• pp.901-911
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• 2009

In this paper, we propose a construction technique of two-level composite gradient map to automatically track a face with large movement in successive frames. Our method is composed of three main steps. First, the gradient maps with two-level resolution are generated for fast convergence of active contour. Second, to recognize the variations of face between successive frames and remove the neighbor background, weighted composite gradient map is generated by combining the composite gradient map and difference mask of previous and current frames. Third, to prevent active contour from converging local minima, the energy slope is generated by using closing operation. In addition, the fast closing operation is proposed to accelerate the processing time of closing operation. For performance evaluation, we compare our method with previous active contour model-based face tracking methods using a visual inspection, robustness test and processing time. Experimental results show that our method can effectively track the face with large movement and robustly converge to the optimal position even in frames with complicated background.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.484-493
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• 2012

Since the 1980s, there have been many research activities devoted to quantitatively characterizing and imaging human tissues based on sound speed, attenuation coefficient, density, nonlinear B/A parameter, etc., but those efforts have not yet reached the stage of commercialization. However, a new imaging technology termed elastography, which was proposed in the early 1980s, has recently been implemented in commercial clinical ultrasound scanners, and is now being used to diagnose prostates, breasts, thyroids, livers, blood vessels, etc., more quantitatively as a complementary adjunct modality to the conventional B-mode imaging. The purpose of this article is to introduce and review various elastographic algorithms for use in quasistatic or static compression type elasticity imaging modes. Most of the algorithms are based on the crosscorrelation or autocorrelation function methods, and the fundamental difference is that the time shift is estimated by changing the lag variable in the former, while it is directly obtained from the phase shift at a fixed lag in the latter.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.31-42
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• 2022

This study verified numerical analysis of the liquefaction phenomenon using LEAP-2017 international round-robin centrifuge test results. Dynamic centrifuge test is performed by applying a 1 Hz tapered sine wave to the model soil deposit, which was formed under a water table in a surface slope of 5° using Ottawa F-65 sand. A numerical model was made on a prototype scale and analyzed using the finite difference method in 2D and 3D conditions. The analyses were verified for acceleration and pore-water pressure histories with depth and residual displacement. Verification results revealed that all numerical liquefaction models agree reasonably with the test result for acceleration histories but not for pre-water pressure histories. Numerical analyses showed much smaller residual displacement than the centrifuge test. Thus, it is necessary to compare the results of numerical analysis with the centrifuge test performed by other institutes in the future.

• Explosives and Blasting
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• v.30 no.2
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• pp.29-42
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• 2012

Variables influencing the free face movement due to rock blasting include the physical and mechanical properties, in particular the discontinuity characteristics, explosive type, charge weight, burden, blast-hole spacing, delay time between blast-holes or rows, stemming conditions. These variables also affects the blast vibration, air blast and size of fragmentation. For the design of surface blasting, the priority is given to the safety of nearby buildings. Therefore, blast vibration has to be controlled by analyzing the free face movement at the surface blasting sites and also blasting operation needs to be optimized to improve the fragmentation size. High-speed digital image analysis enables the analyses of the initial movement of free face of rock, stemming optimality, fragment trajectory, face movement direction and velocity as well as the optimal detonator initiation system. Even though The high-speed image analysis technique has been widely used in foreign countries, its applications can hardly be found in Korea. This thesis aims at carrying out a fundamental study for optimizing the blast design and evaluation using the high-speed digital image analysis. A series of experimentation were performed at two large surface blasting sites with the rock type of shale and granite, respectively. Emulsion and ANFO were the explosives used for the study. Based on the digital images analysis, displacement and velocity of the free face were scrutinized along with the analysis fragment size distribution. In addition, AUTODYN, 2-D FEM model, was applied to simulate detonation pressure, detonation velocity, response time for the initiation of the free face movement and face movement shape. The result show that regardless of the rock type, due to the displacement and the movement velocity have the maximum near the center of charged section the free face becomes curved like a bow. Compared with ANFO, the cases with Emulsion result in larger detonation pressure and velocity and faster reaction for the displacement initiation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.2
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• pp.141-147
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• 1995

Various numerical models for predicting wave deformation have been proposed. Among them a time-dependent mild-slope equation based on the line discharges and surface-elevation changes has been widely used in the wave fields with reflective waves. If applying this model to the case of obliquely-incident waves, not only the open-sea boundary but also one of the lateral boundaries should be treated as incident boundaries. In this study, Maruyama and Kajima (1985), Copeland (1985) and Ohnaka and Watanabe (1987)'s method are reviewed and the characteristics of these methods are analyzed using e normalized wave heights, wave angels and phases obtained from the numerical experiments. It is shown that Ohnaka and Watanabe(1987)'s method provides the most adequate driving boundary is the most suitable in e wave field with a general bottom slope.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.317-327
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• 2001

In this paper, a relation to calculate design moments for reinforced concrete(RC) bridges constructed by movable scaffolding system(MSS) is introduced. Through the time-dependent analysis of RC bridges considering the construction sequence, the structural responses related to the member forces and deflections are reviewed, and a governing equation for determination of the design moment, which includes the creep deformation, is derived on the basis of the displacement-force condition at every constructuion stage. By using the relation, the design moment and its variation over time can easily be obtained only with the elastic analysis results without additional time-dependent analysis. In addition, correlation studies with the results by rigorous numerical analyses are conducts to verify the applicability of the introduced relation, and a more reasonable guideline for the determination of design moments is proposed on the basis of the obtained moment envelop.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.5
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• pp.445-458
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• 2014

The displacement data monitored during tunnel construction play a crucial role in predicting the behaviour of ground around and ahead of excavation face. However, the management criteria for monitoring data are not well established especially for the reliable analysis on varying aspect of displacement data along with chainage. In this study, we evaluated the applicability of x-MR control chart method, which is kind of applied statistical management method, for the analysis of displacement monitoring data in terms of prediction of possible collapse or induced cracks. As a result, a possible abnormal behaviour could be predicted beforehand at 5 ~ 13 m ahead or on at least one day before it occurred by using x-MR control chart method. In addition, it is noted that the moving range for the x-MR control chart should be set to 5~10 for this purpose.